.SS "DPIF-NETDEV COMMANDS"
These commands are used to expose internal information (mostly statistics)
about the "dpif-netdev" userspace datapath. If there is only one datapath
(as is often the case, unless \fBdpctl/\fR commands are used), the \fIdp\fR
argument can be omitted. By default the commands present data for all pmd
threads in the datapath. By specifying the "-pmd Core" option one can filter
the output for a single pmd in the datapath.
.
.IP "\fBdpif-netdev/pmd-stats-show\fR [\fB-pmd\fR \fIcore\fR] [\fIdp\fR]"
Shows performance statistics for one or all pmd threads of the datapath
\fIdp\fR. The special thread "main" sums up the statistics of every non pmd
thread.

The sum of "emc hits", "smc hits", "megaflow hits" and "miss" is the number of
packet lookups performed by the datapath. Beware that a recirculated packet
experiences one additional lookup per recirculation, so there may be
more lookups than forwarded packets in the datapath.

Cycles are counted using the TSC or similar facilities (when available on
the platform). The duration of one cycle depends on the processing platform.

"idle cycles" refers to cycles spent in PMD iterations not forwarding any
any packets. "processing cycles" refers to cycles spent in PMD iterations
forwarding at least one packet, including the cost for polling, processing and
transmitting said packets.

To reset these counters use \fBdpif-netdev/pmd-stats-clear\fR.
.
.IP "\fBdpif-netdev/pmd-stats-clear\fR [\fIdp\fR]"
Resets to zero the per pmd thread performance numbers shown by the
\fBdpif-netdev/pmd-stats-show\fR and \fBdpif-netdev/pmd-perf-show\fR commands.
It will NOT reset datapath or bridge statistics, only the values shown by
the above commands.
.
.IP "\fBdpif-netdev/pmd-perf-show\fR [\fB-nh\fR] [\fB-it\fR \fIiter_len\fR] \
[\fB-ms\fR \fIms_len\fR] [\fB-pmd\fR \fIcore\fR] [\fIdp\fR]"
Shows detailed performance metrics for one or all pmds threads of the
user space datapath.

The collection of detailed statistics can be controlled by a new
configuration parameter "other_config:pmd-perf-metrics". By default it
is disabled. The run-time overhead, when enabled, is in the order of 1%.

.RS
.IP
.PD .4v
.IP \(em
used cycles
.IP \(em
forwared packets
.IP \(em
number of rx batches
.IP \(em
packets/rx batch
.IP \(em
max. vhostuser queue fill level
.IP \(em
number of upcalls
.IP \(em
cycles spent in upcalls
.PD
.RE
.IP
This raw recorded data is used threefold:

.RS
.IP
.PD .4v
.IP 1.
In histograms for each of the following metrics:
.RS
.IP \(em
cycles/iteration (logarithmic)
.IP \(em
packets/iteration (logarithmic)
.IP \(em
cycles/packet
.IP \(em
packets/batch
.IP \(em
max. vhostuser qlen (logarithmic)
.IP \(em
upcalls
.IP \(em
cycles/upcall (logarithmic)
The histograms bins are divided linear or logarithmic.
.RE
.IP 2.
A cyclic history of the above metrics for 1024 iterations
.IP 3.
A cyclic history of the cummulative/average values per millisecond wall
clock for the last 1024 milliseconds:
.RS
.IP \(em
number of iterations
.IP \(em
avg. cycles/iteration
.IP \(em
packets (Kpps)
.IP \(em
avg. packets/batch
.IP \(em
avg. max vhost qlen
.IP \(em
upcalls
.IP \(em
avg. cycles/upcall
.RE
.PD
.RE
.IP
.
The command options are:
.RS
.IP "\fB-nh\fR"
Suppress the histograms
.IP "\fB-it\fR \fIiter_len\fR"
Display the last iter_len iteration stats
.IP "\fB-ms\fR \fIms_len\fR"
Display the last ms_len millisecond stats
.RE
.IP
The output always contains the following global PMD statistics:
.RS
.IP
.EX
Time: 15:24:55.270
Measurement duration: 1.008 s

pmd thread numa_id 0 core_id 1:

  Iterations:              572817  (1.76 us/it)
  - Used TSC cycles:   2419034712  ( 99.9 % of total cycles)
  - idle iterations:       486808  ( 15.9 % of used cycles)
  - busy iterations:        86009  ( 84.1 % of used cycles)
  Rx packets:             2399607  (2381 Kpps, 848 cycles/pkt)
  Datapath passes:        3599415  (1.50 passes/pkt)
  - EMC hits:              336472  (  9.3 %)
  - SMC hits:                   0  ( 0.0 %)
  - Megaflow hits:        3262943  ( 90.7 %, 1.00 subtbl lookups/hit)
  - Upcalls:                    0  (  0.0 %, 0.0 us/upcall)
  - Lost upcalls:               0  (  0.0 %)
  Tx packets:             2399607  (2381 Kpps)
  Tx batches:              171400  (14.00 pkts/batch)
.EE
.RE
.IP
Here "Rx packets" actually reflects the number of packets forwarded by the
datapath. "Datapath passes" matches the number of packet lookups as
reported by the \fBdpif-netdev/pmd-stats-show\fR command.

To reset the counters and start a new measurement use
\fBdpif-netdev/pmd-stats-clear\fR.
.
.IP "\fBdpif-netdev/pmd-perf-log-set\fR \fBon\fR|\fBoff\fR \
[\fB-b\fR \fIbefore\fR] [\fB-a\fR \fIafter\fR] [\fB-e\fR|\fB-ne\fR] \
[\fB-us\fR \fIusec\fR] [\fB-q\fR \fIqlen\fR]"
.
The userspace "netdev" datapath is able to supervise the PMD performance
metrics and detect iterations with suspicious statistics according to the
following criteria:
.RS
.IP \(em
The iteration lasts longer than \fIusec\fR microseconds (default 250).
This can be used to capture events where a PMD is blocked or interrupted for
such a period of time that there is a risk for dropped packets on any of its Rx
queues.
.IP \(em
The max vhost qlen exceeds a threshold \fIqlen\fR (default 128). This can be
used to infer virtio queue overruns and dropped packets inside a VM, which are
not visible in OVS otherwise.
.RE
.IP
Such suspicious iterations can be logged together with their iteration
statistics in the \fBovs-vswitchd.log\fR to be able to correlate them to
packet drop or other events outside OVS.

The above command enables (\fBon\fR) or disables (\fBoff\fR) supervision and
logging at run-time and can be used to adjust the above thresholds for
detecting suspicious iterations. By default supervision and logging is
disabled.

The command options are:
.RS
.IP "\fB-b\fR \fIbefore\fR"
The number of iterations before the suspicious iteration to be logged
(default 5).
.IP "\fB-a\fR \fIafter\fR"
The number of iterations after the suspicious iteration to be logged
(default 5).
.IP "\fB-e\fR"
Extend logging interval if another suspicious iteration is detected
before logging occurs.
.IP "\fB-ne\fR"
Do not extend logging interval if another suspicious iteration is detected
before logging occurs (default).
.IP "\fB-q\fR \fIqlen\fR"
Suspicious vhost queue fill level threshold. Increase this to 512 if the Qemu
supports 1024 virtio queue length (default 128).
.IP "\fB-us\fR \fIusec\fR"
Change the duration threshold for a suspicious iteration (default 250 us).
.RE

Note: Logging of suspicious iterations itself consumes a considerable amount
of processing cycles of a PMD which may be visible in the iteration history.
In the worst case this can lead OVS to detect another suspicious iteration
caused by logging.

If more than 100 iterations around a suspicious iteration have been logged
once, OVS falls back to the safe default values (-b 5 -a 5 -ne) to avoid
that logging itself continuously causes logging of further suspicious
iterations.
.
.IP "\fBdpif-netdev/pmd-rxq-show\fR [\fB-pmd\fR \fIcore\fR] [\fIdp\fR]"
For one or all pmd threads of the datapath \fIdp\fR show the list of queue-ids
with port names, which this thread polls.
.
.IP "\fBdpif-netdev/pmd-rxq-rebalance\fR [\fIdp\fR]"
Reassigns rxqs to pmds in the datapath \fIdp\fR based on their current usage.
